Depending on the size of the fountain and whether you can extend a hose
below the water level, you could use a siphon hose with sufficient
diameter to also handle the debris.
Start the siphon by submerging the entire hose, making sure that no air
is in the hose. Hold your finger or palm of your hand over one end of
the hose while taking it out of the water and extending it over the edge
and below the water level. A 1.5 inch pool vacuum hose will drain a 400
gallon spa in about 10 minutes. Work quickly if you just want to remove
debris without completely draining the fountain.